In this paper, by taking four M_S≥7.8 earthquakes in China continent since the 1960s as research object, the authors investigated the aftershock activity and its classification of great earthquakes around M_S8.0, the physical-mechanical causes of the differentiated features of aftershock sequences are also discussed based on the rheology model. Some preliminary conclusions are drawn: 1) the types of aftershock sequences can be divided into low activity sequence type and high activity sequence type; 2) the differentiated features of aftershock sequences are closely related to the process of the main shock preparation; and 3) the rheological property of media in seismogenic zone and the high or low velocity of tectonic deformation may be the important causes of the differentiated features.